Offshore well workover method



May 26, 1970 w. H. PETERSEN 3,513,911

OFFSHORE WELL WORKOVER METHOD Filed May 24. 1968 2 Sheets-Sheet 1INVENTOR:

WILLIAM H. PETERSEN aYcfl yggr HIS ATE QRNEY May 26, 1970 w. H. PETERSEN5 OFFSHORE WELL WORKOVER METHOD Filed May 24, 1968 2 Sheets-Sheet 2INVENTOR= WILLIAM H. PETERSEN HIS ATTORNEY United States Patent3,513,911 OFFSHORE WELL WORKOVER METHOD William H. Petersen, Houston,Tex., assignor to Shell Oil Company, New York, N.Y., a corporation ofDelaware Filed May 24, 1968, Ser. No. 731,993 Int. Cl. E21b 7/12; E21c19/00 US. Cl. 166-.6 2 Claims ABSTRACT OF THE DISCLOSURE A method oflowering apparatus to an underwater wellhead assembly from a floatingvessel, attaching the apparatus to the wellhead assembly, establishingguidelines between the vessel and a structure on the ocean floor, andretrieving at least a portion of the attached wellhead assembly to thevessel along the guidelines by said apparatus.

This invention relates to a method of carrying out operations withrespect to underwater wells at deep water locations from a floatingvessel.

More particularly, the present invention relates to a method ofestablishing contact between an apparatus lowerable from a floatingvessel and an underwater wellhead structure whereby guideline means areestablished between the vessel and the structure and at least a portionof a wellhead assembly may be retrieved along said guidelines. Theaforesaid operations may be carried out remotely from said vessel.

During recent years, the continued search for oil has resulted indeveloping methods and apparatus for drilling underwater wells atlocations where the water may range from 100 to 1,500 feet or more indepth. In these locations, it has become the widespread practice toposition a wellhead at a considerable distance below the surface of thewater, preferably on the ocean floor, so that it is not a hazard tonavigation of ships in the area.

One method of drilling and completing an underwater well on the oceanfloor is described in US. Pat. No. 3,256,937, issued to J. A. Haeber etal. on June 21, 1966. In the method described in that patent, a wellheadstructure, including a wellhead assembly, is positioned on an underwaterwellhead and a series of guidelines extend from the wellhead structureto a drilling barge or other drilling vessel floating on the surface ofthe water. Through the use of the guidelines various pieces of equipmentare raised and lowered between the wellhead structure and the vessel.After well drilling operations have been completed, the guide cables areleft permanently attached to the wellhead structure at their lower endsand are secured, preferably to a buoy, at their upper ends, with thebuoy floating on the surface of the water, whereby they may be usedsubsequently to reestablish contact with the structure. Alternatively,the cables are dropped to the ocean floor from which they are recoveredlater by means of grappling hooks or other suitable means. Since cableslying on the ocean floor tend to become entangled as well asconstituting a hazard to sea traflic, it is desired that these guidecables be removed when drilling operations have been completed.

It is, of course, necessary to periodically perform workover ormaintenance operations with respect to an underwater well and associatedwellhead assembly. Accordingly, special wellhead assemblies have beendesigned and constructed that can be readily removed from the underwaterwellhead and raised to the surface. One underwater wellhead structure ofthis type is shown and described in US Pat. No. 3,064,735, issued Nov.20, 1962, to R. J. Bauer et al. To insure the safe and rapid transportof the wellhead assembly to the surface, as

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well as to provide means whereby it may be returned to the underwaterwellhead after the desired operations have been performed, some form ofguide means is preferably disposed between the vessel and the underwaterwellhead. As previously stated, however, the common practice is toremove guide cables or guidelines from the underwater wellhead structurewhen drilling operations have been completed.

SUMMARY OF THE INVENTION It is therefore a primary object of thisinvention to provide a method whereby guideline means are remotelyestablished between an underwater wellhead structure and a floatingvessel and at least a portion of a wellhead assembly is removed to thevessel along the guidelines.

A still further object of the present invention is to provide a methodwhereby retrieval apparatus and guide carrying means are substantiallysimultaneously lowered from a floating vessel to an underwater wellheadstructure whereby the retrieval apparatus is attached to a wellheadassembly, guidelines are established between the vessel and thestructure, and at least a portion of the assembly is pulled to thevessel by the retrieval apparatus.

The above objects have been attained in the present invention byproviding a method of retrieving at least a portion of an underwaterproduction wellhead assembly, comprising part of an underwaterstructure, to the surface of a body of water wherein retrieval apparatusand guide-carrying means are lowered from a vessel and positioned on apreviously located assembly. The retrieval apparatus is then connectedto the assembly and guide means are lowered from the guide carryingmeans and connected to the remainder of the structure. The portion ofthe wellhead assembly to be retrieved is then disconnected from theremainder of the structure and pulled to the water surface along theguide means.

DESCRIPTION OF THE DRAWING These and other objects of the invention willbe understood from the following description taken with reference to thedrawing wherein:

FIG. 1 is a diagrammatic, frontal view taken on longitudinal projectionillustrating a vessel floating on a body of water with retrievalapparatus and guide carrying means depending therefrom and positionedover an underwater wellhead structure, including a wellhead assembly;

FIG. 2 is a diagrammatic, side view taken on longitudinal projection ofthe retrieval apparatus, guide carrying means, and underwater wellheadstructure, in the relative positions illustrated in FIG. 1;

FIGS. 3 and 4 are diagrammatic, frontal views taken on longitudinalprojection showing the relative positions of the retrieval apparatus,guide carrying means and underwater wellhead structure during variousstages in the operation thereof while carrying out the steps of themethod according to the present invention; and

FIG. 5 is a diagrammatic, side view taken on longitudinal projectionshowing thte wellhead assembly portion of the wellhead structure beingpulled to the surface of the body of water by the retrieval apparatusalong guidelines attached to the wellhead structure.

Referring to FIG. 1 of the drawing, a workover vessel, barge, orplatform 11, of any suitable floatable type, is illustrated as floatingon the surface of a body of water 12 while being substantially fixedlypositioned over a preselected well location by suitable vesselpositioning means well known to the art, or by being anchored to the seabed 13 by anchor lines 14 and 15 running to anchors (not shown).Equipment of this type may be used when carrying out underwater wellworkover operations in water depths varying from about to 1500 feet ormore. The

workover vessel 11 is equipped with a suitable derrick 16 as well asother auxiliary equipment needed for operations of this type. Thederrick 16 is positioned over a slot or well 17 which extends verticallythrough the vessel in a conventional manner. When carrying out thevarious steps of the method according to the present invention, the slot17 of the vessel may be either centrally located or extend in from oneedge. However, operations may be carried out over the side of the bargeor vessel without the use of a slot. Additionally, it is to beunderstood that the method of the present invention may be used alsowhen performing operations with respect to a well from any suitableoperational base positioned above the surface of the water, such as, forexample, from a barge having legs extending to the ocean floor or from aplatform permanently positioned on the ocean floor.

An underwater wellhead structure 18 is located on the sea bed 13 belowvessel 11. It is to be assumed that the vessel has been positioned asillustrated through the use of conventional navigational aids andanchored. The wellhead structure 18 includes a base member 19 having apair of upstanding guide posts 20 and 21 fixedly mounted thereon. A wellcasing 22, which extends into the sea bed 13 as shown, and is preferablyfixedly secured therein as by means of cement 23, passes through basemember 19 and terminates at its upper end with wellhead member 24. Aproduction wellhead assembly 25 is mounted on wellhead member 24.Although the method according to the present invention may be carriedout with a wellhead assembly construction of any suitable type, for easeof explanation and convenience, it will be assumed that wellheadassembly 25 will be of the type disclosed in afore mentioned US. Pat.No. 3,064,735. As with the wellhead assembly disclosed therein, assembly25 is of a Y-branched construction and includes a central body havingfluid flow handling conduits 26 and 27 extending therefrom whichcommunicate, respectively, with production conduits 28 and 29 extendinginto the well within casing 22. The outer ends of conduits 26 and 27terminate at connectors 30 and 31 as shown. The connectors may be of anysuitable remotely-detachable type, one example of which is disclosed inUS. Pat. -No. 3,052,299, issued Sept. 4, 1962, to Geer et al. Theconnectors 30 and 31 establish fluid flow communication between conduits26 and 27 and production flow lines, such as flow line 32 (FIG. 2),which are positioned on sea bed 13 and lead to a suitable storagefacility (not shown) in the usual manner.

Depending from vessel 11 by means of pipe string 33 is an arrangementcomprising a retrieval apparatus 34 and guide carrying means 35. Theparticular arrangement shown is disclosed in copending US. applicationSer. No. 731,382, filed May 23, 1968, and is set forth here forillustration purposes only. It is to be understood that other suitablearrangements may be utilized in carrying out the steps according to thepresent invention. As is set forth in more detail in the aforementionedU.S. application Ser. No. 731,382, retrieval apparatus 34 includes lockmeans (not shown) operative upon positioning of the retrieval apparatusupon production wellhead assembly 25 to lock the retrieval apparatus tothe wellhead assembly. As is also shown in greater detail in thelast-mentioned US. application, guide carrying means 35 includes a pairof cylindrical housing members 36 and 37 which are frame-mounted onretrieval apparatus 34. Slidably mounted in housing members 36 and 37are elongated connector elements 38 and 39, respectively, whichterminate at their lower ends in cone-shaped members 40 and 41. Suitablelatching means, such as latching member 4111 (FIG. are disposed incone-shaped members 40 and 41 and are connected to guidelines 42 and 43(FIG. 1) which extend to vessel -11 in the manner illustrated.Guidelines 42 and 43, respectively, are operatively associated withconstant tension hoists 44 and 45 disposed on vessel 11. As is shown inaforementioned US. application, Ser. No. 731,382, the constant tensionapplied to guidelines 42 and 4 43 serves to retain cone-shaped members40 and 41 against the lower ends of housing members 36 and 37 and thelatching means seated within the cone-shaped members The methodaccording to the present invention will now be described. Again,although such method will be described with particular reference to theapparatus shown in the drawings, the method steps may be carried outthrough the use of other desired means consistent with the requirementsof practice or the exigencies of given conditions.

After the retrieval apparatus and guide-carrying means have beenassembled in the manner shown in FIG. 1, the assembled unit is loweredfrom vessel 11 by lengthening pipe string 33 in the customary manner,i.e., through the addition of individual pipe sections to the string.Throughout this lowering operation, constant tension is maintained onguidelines 42 and 43 by hoists 44 and 45, thereby retaining the latchingmembers within coneshaped members 40 and 41 and keeping the cone-shapedmembers in contact with the lowermost ends of housing members 36 and 37.The arrangement comprising the retrieval apparatus and the guidecarrying means is lowered until it has been determined that thelowermost portion thereof is positioned a distance from the sea bed 13somewhat greater than the height of the production wellhead assembly 18,as shown in FIGS. 1 and 2. At this point, wellhead assembly locatingmeans, such as sonar unit 46 and/or television camera 47, are actuatedand monitored from the vessel 11 in the customary manner. Using thisinformation, the operator then positions the retrieval apparatusdirectly over the wellhead assembly in any known manner, such as bymanipulating the pipe string.

Still further lowering of the retrieval apparatus and guide carryingmeans then brings the retrieval apparatus into engagement with theunderwater wellhead assembly as shown in FIG. 3. Outwardly flangedmember 48 is preferably provided on the lower end of the retrievalapparatus to assist in properly axially aligning retrieval apparatus 34over wellhead assembly 18 as it is lowered thereupon. Although notillustrated herein, cooperating orienting means will preferably beprovided on said retrieval apparatus and said wellhead assembly to alsorotatably align the retrieval apparatus to a predetermined position withrespect to the assembly as the retrieval apparatus is lowered. Suitablyorienting means for this purpose are disclosed in US. application, Ser.No. 731,382, wherein a pin on the retrieval apparatus operates with aslot on the wellhead assembly to effect rotatable movement. When thelowering operation has been completed and the retrieval apparatus andthe wellhead assembly are located relative to each other as shown inFIG. 3, the lock means (not shown) associated with the retrievalapparatus is actuated to lockingly engage the retrieval apparatus to thewellhead assembly.

It should be noted that when the retrieval apparatus has beenpositioned, oriented, and locked, as previously described, with respectto the wellhead assembly, housing members 36 and 37 of the guidecarrying means are axially positioned over upstanding guideposts 20 and21. By releasing the tension on guidelines 42 and 43, cone-shapedmembers 40 and 41 with their respective latching members are droppedover guideposts 20' and 21 as shown in FIG. 4 under the influence ofgravity. The latching members are then automatically latched by means ofany suitable mechanism to the guideposts. At this point, the requiredremote disconnect operations are made with respect to the wellheadassembly to close down the well and enable at least a portion of theWellhead assembly to be raised to the surface of the water. Theoperation of the various valves, latches, etc. involved when performingsuch disconnects may be effected by use of any known expedient, such ashydraulic or electric conduits extending from vessel 11.

FIG. 5 illustrates the operation of raising at least a portion of thewellhead assembly to the surface after required disconnects have beenmade as discussed in the preceding paragraph. In this instance, theentire assembly 18 is being pulled to vessel 11 from wellhead member 24by means of pipe string 33 and retrieval apparatus 34. It should benoted that the flow handling conduits, such as conduit 27, have beendisconnected from their respective flow lines, such as line 32. Thelatching members, such as latching member 41a, remain attached to theirrespective guideposts as the wellhead assembly portion is pulledupwardly with guidelines 42 and 43 cooperating with housing members 36and 37 to guide the upward course of movement of the retrieval apparatus34, guide carrying means 35, and said wellhead assembly portion. Afterthe wellhead assembly portion has been repaired or wholly or partiallyreplaced, the guidelines 42 and 43 may be subsequently used to guide itinto position on the wellhead as the lowering thereof is etfected, suchas by lowering it by means of a pipe string.

I claim as my invention:

1. A method of retrieving to the surface of a body of water at least aportion of an underwater production wellhead assembly, said assemblycomprising part of an underwater wellhead structure, said methodcomprising:

assembling together retrieval apparatus and guide-carrying means;

simultaneously lowering the assembled retrieval apparatus andguide-carrying means from a vessel floating on the surface of a body ofwater while maintaining said assembled retrieval apparatus andguide-carrying means operatively disassociated from said underwaterwellhead assembly;

locating said underwater wellhead assembly;

positioning said retrieval apparatus in engagement with said underwaterwellhead assembly;

orienting said retrieval apparatus to a predetermined rotatable positionwith respect to said Wellhead assembly;

connecting said retrieval apparatus to said wellhead assembly; loweringguide means from said guide carrying means; connecting said guide meansto the remainder of said underwater wellhead structure; I disconnectingat least a portion of said wellhead assembly from said remainder of saidstructure with said portion attached to said retrieval apparatus;

raising said retrieval apparatus and the attached portion .of saidwellhead assembly to the floating vessel; and

guiding the retrieval apparatus and the attached portion of the wellheadassembly along said guide means as the retrieval apparatus and theattached portion of the wellhead assembly are being raised to thevessel.

2. The method of claim 1 wherein the connecting of said guide means tothe remainder of said structure is carried out by dropping the guidemeans from said guide carrying means and permitting the guide means tofall under the influence of gravity until operative engagement is madebetween the guide means and the remainder of the structure.

References Cited UNITED STATES PATENTS 3,021,909 2/196-2 Postlewaite 73,050,140 8/1962 Hayes 175-7 3,064,735 11/ 196-2 Bauer et a1. 166-.63,166,123 1/ 1965 Watkins 166-.6 3,23 6,302 2/ 1966 Postlewaite 1757 XNILE C. BYERS, Sn, Primary Examiner R. E. FAVREAU, Assistant ExaminerUS. Cl. X.R. 1757

